STL Algorithm

Algorithm Used in Vector

(i) Non-Manipulating Algorithms:

          1. sort(first_iterator,last_iterator)-To sort a given vector.

          2. reverse(first_iterator,last_iterator)-To reverse a given vector.

          3. *max_element(first_iterator,last_iterator)-To find the maximum element of a vector

          4. *min_element(first_iterator,last_iterator)-To find the minimum element of a vector 

          5. accumulate(first_iterator,last_iterator.initial value of sum)-Does the summation of vector elements.

          6. count(first_iterator,last_iterator,x)-Count the occurrence in vector.

          7. find(first_iterator,last_iterator,x)-Points the last address of the vector if the element is not found

Sample Code:

	#include<bits/stdc++.h>
	using namespace std;
	int main()
	{
	//freopen("input.txt","r",stdin);
	//freopen("output.txt","w",stdout);
	vector<int>v;
	int i,a,n,w;
	cin>>n; //Number of element in the vector
	for(i=0;i<n;i++){
	cin>>a;
	v.push_back(a);
	}
	sort(v.begin(),v.end());
	cout<<"After sorting in Ascending order:\n";
	for(auto x:v)cout<<x<<' ';cout<<endl;
	reverse(v.begin(),v.end());
	cout<<"\nAfter reversing:\n";
	for(auto x:v)cout<<x<<' ';cout<<endl;
	cout<<"\nMaximum element in the vector:\n";
	cout<<*max_element(v.begin(),v.end())<<endl;
	cout<<"\nMinimum element in the vector:\n";
	cout<<*min_element(v.begin(),v.end())<<endl;
	cout<<"\nSummation of the elements in the vector:\n";
	cout<<accumulate(v.begin(),v.end(),0)<<endl;
	cout<<"\nOccurrence of the a number\n";
	cout<<count(v.begin(),v.end(),2)<<endl;
	cout<<"\nFinding the position of a number in the vector\n";
	if(find(v.begin(),v.end(),2)!=v.end()){
	cout<<"Element found at\n";
	auto q=find(v.begin(),v.end(),2);
	cout<<q-v.begin()<<endl;
	}
	else cout<<"Element not found\n";
	return 0;
	}
	Input:
	7
	1 3 2 4 5 2 2
	Output:
	After sorting in Ascending order:
	1 2 2 2 3 4 5
	After reversing:
	5 4 3 2 2 2 1
	Maximum element in the vector:
	5
	Minimum element in the vector:
	1
	Summation of the elements in the vector:
	19
	Occurrence of the a number
	3
	Finding the position of a number in the vector
	Element found at
	3

view raw STL Algorthm1.cpp hosted with ❤ by GitHub

       
          8. binary_search(first_iterator,last_iterator,x)-Tests whether x exists in the sorted vector or not!
          9. lower_bound(first_iterator,last_iterator,x)- The leftmost position in which 'x' can be inserted keeping the vector sorted.
          10. upper_bound(first_iterator,last_iterator,x)- The rightmost position in which 'x' can be inserted keeping the vector sorted.

Sample Code:

	#include<bits/stdc++.h>
	using namespace std;
	int main()
	{
	//freopen("input.txt","r",stdin);
	//freopen("output.txt","w",stdout);
	vector<int>v;
	int n,i,a;
	cin>>n;
	for(i=0;i<n;i++){
	cin>>a;
	v.push_back(a);
	}
	sort(v.begin(),v.end());
	auto low=lower_bound(v.begin(),v.end(),20);
	auto up=upper_bound(v.begin(),v.end(),20);
	cout<<"The lower bound is at position: "<<low-v.begin()<<endl;
	cout<<"The upper bound is at position: "<<up-v.begin()<<endl;
	return 0;
	}
	Input:
	8
	5 10 15 20 20 23 42 45
	Output:
	The lower bound is at position: 3
	The upper bound is at position: 5

view raw upperlower.cpp hosted with ❤ by GitHub

       
 (ii) Manipulating Algorithms:
           1. vect.erase(position to be deleted)-This erases the selected element and shifts and resizes the vector.
           2. vect.erase(unique(vect.begin(),vect.end()),vect.end())-This erases thye duplicate occurrence in the sorted vector.
           3. next_permutation(first_iterator,last_iterator)-This modified vector to it's next permutation.
           4. prev_permutation(first_iterator,last_iterator)-This modified vector to it's previous permutation.

Sample Code:

	#include<bits/stdc++.h>
	using namespace std;
	int main()
	{
	//freopen("input.txt","r",stdin);
	//freopen("output.txt","w",stdout);
	vector<int>vect;
	int n,i,a;
	cin>>n;
	for(i=0;i<n;i++){
	cin>>a;
	vect.push_back(a);
	}
	sort(vect.begin(),vect.end());
	cout<<"After sorting in Ascending order\n";
	for(auto x:vect) cout<<x<<' '; cout<<endl;
	vect.erase(vect.begin()+1);
	cout<<"After removing 1th element\n";
	for(auto x:vect)cout<<x<<' '; cout<<endl;
	vect.erase(unique(vect.begin(),vect.end()),vect.end());
	cout<<"After removing duplicate elements\n";
	for(auto x:vect)cout<<x<<' '; cout<<endl;
	next_permutation(vect.begin(),vect.end());
	cout<<"After performing next permutation:\n";
	for(auto x:vect) cout<<x<<' '; cout<<endl;
	prev_permutation(vect.begin(),vect.end());
	cout<<"After performing prev permutation:\n";
	for(auto x:vect) cout<<x<<' '; cout<<endl;
	return 0;
	}
	Input:
	7
	4 3 1 2 7 1 1
	Output:
	After sorting in Ascending order
	1 1 1 2 3 4 7
	After removing 1th element
	1 1 2 3 4 7
	After removing duplicate elements
	1 2 3 4 7
	After performing next permutation:
	1 2 3 7 4
	After performing prev permutation:
	1 2 3 4 7

view raw Next permutation.cpp hosted with ❤ by GitHub

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